The present invention relates generally, as indicated, to improvements in engines and, more particularly, to linear engine/hydraulic pumps. Linear engines are well known and typically include a piston movable in an engine cylinder in response to internal combustion occurring in the latter and means for removing output work from the piston during its power stroke. In particular, such output work is removed substantially directly from the linearly moving piston without conversion through a crankshaft to rotary motion and then, for example, back to linear motion, say to operate a pump. The combination of a linear engine/hydraulic pump as a substantially integral unit also is a known device in which output work from the linear engine directly operates one or more pump pistons that pump fluid received at relatively low pressure to a relatively high pressure fluid output, say to provide hydraulic work input to a hydraulic motor.
To provide motive power for heavy duty vehicles, such as an armored combat vehicle, conventional relatively heavy duty engines, i.e. of the type that produce a rotary output force, and transmissions have been used. In the past hydrostatic transmissions have been evaluated for use in such heavy duty vehicles, but the relatively low efficiency associated with a variable displacement pump and motor combination driven by a conventional engine, which produces a rotary output, has precluded such use. In the past the inherent advantages of hydrostatic systems have been more than offset in the negative by the larger quantities of fuel and the larger cooling systems required in the vehicle in comparison to the requirements of a conventional engine and transmission for providing motive power thereto.